This invention relates to a cutting tool for cutting a series of depressions along surfaces of roadways, and more particularly to a cutting tool utilizing a flywheel gearbox design.
As motor vehicle operators become fatigued or distracted, the possibility of the vehicle drifting off the road or over the center line and into the opposite lane of traffic increases, either of which can potentially lead to disastrous results. To minimize this occurrence, a series of depressions are cut along the shoulders or center line of the roadway, referred to as ground in rumble strips. The purpose of the rumble strip is to alert drivers when they have drifted outside their traffic lane by creating a sound and causing vibration of the vehicle as the vehicle tires travel over the depressions.
Differing designs of road surface grinders/cutting machines which use a cutting drum or drums to cut individual depressions have heretofore been devised. In older designs, cutting drums have been attached to or made part of a multipurpose power unit such as a tractor or skidsteer loader. The tractor or skidsteer loader is used to move the cutting drum along the surface of the road and to provide any necessary utilities thereto, such as electricity or hydraulic fluid. More recent designs have attached the cutting drum to a vehicle frame designed solely for use with the cutting drum. With either design, the cutting drum is lowered into contact with the road surface to cut the depression.
Current practice cutting machines use a variety of methods for engaging and disengaging the cutting drum into the road surface to cut the depression and for repositioning the cutting drum for the next cut. One method of raising and lowering the cutting drum requires an operator to manually control a hydraulic cylinder which is connected to the cutting drum. A problem with this method is that it is difficult for the operator to move the cylinder controls quickly enough to achieve a sufficient production rate (defined as forward feet per minute) while cycling the cutter.
An example of such a manually operated system is disclosed in U.S. Pat. No. 5,094,565 which utilizes a plurality of manually controlled cutting drums to cut a series of depressions at one time. The production rate is increased by using the plurality of cutting drums, which are lowered onto the road surface to cut the depressions while the power unit is stationary. After the cut is complete, the cutting drums are raised and the power unit moves to the next location. Since there is not a continuous forward movement of the power unit, additional time is required for raising and lowering the cutting drums. Additionally, since the required sizing (depth, width, length, and radius of curvature of each depression) is specified depending on the task at hand, appropriately sized cutting drums must be used in order to meet the required dimensional sizing of the depressions. Thus, if different depression sizes are required, the cutting drums may have to be replaced.
In order to overcome some of the problems with the manual systems, automated means for raising and lowering the cutting drum have been developed. Such means include rigidly connecting the cutting drums (1) to an eccentric wheel which rolls over the road surface or (2) to a cam and lever system. In each of these automated systems, the cutting drum is automatically raised and lowered as the power unit moves forward due, respectively, to the rotation of the eccentric wheel and the action of the cam and levers. These systems are an improvement over the manually operated systems since the production rate of making depressions is increased because the cutting drum cuts as the power unit moves forward.
In order to achieve higher production while cycling the cutter, the cutter must maintain a minimum cutter rpm. To achieve the desired product, i.e. a road surface depression of a specified dimension, the cutter must make at least one complete revolution while cutting each rumble strip depression. Less than one full revolution of the cutter produces an incomplete or dimensionally defective cut. In particular, the repeating cycling of the cutter against the road surface produces repeating torque peaks as the cutter initially makes contact with the road surface that must be overcome in order to produce the required full revolution of the cutter per cut.
Therefore, the maximum production rate of any cutting machine is limited by the amount of time required for the cutting drum to complete each cut. In addition, current systems can not meet maximum production rates because of inherent limitations above and beyond the cutting time required by the cutting drum to complete its cut, such as those imposed by the mechanical arrangements used to control cutter rpm and the vertical motion of the grinding drum.
U.S. Pat. No. 5,415,495, assigned to the assignee of the present invention, describes an electronic controller responsive to a signal indicative of the forward distance traveled by the cutter. The controller electronically controls an engaging device so that the cutting drum moves out of and into contact with the road surface in accordance with the distance that the cutting drum moves along the road surface and a specified dimensional profile of the depression, which are stored in the electronic controller.
One problem with this and other current practice hydrostatic drives is the elasticity of hydraulic systems. This problem causes the cutter rpm to drop off as much as 50% during the cut. In order to maintain the required minimum one full cutter rotation per cut, forward speed must be reduced, with resulting decrease in production.
One way to achieve greater production is to increase the cutter rotational speed so that when it slows down on contact with the road surface it effectively still maintains the necessary revolutions per minute to permit at least one full revolution prior to the next cycle. However, in current practice, the cutting teeth are held in their holders solely with springs that create friction. While the springs protect the tooth holder from wear and permit tooth rotation, when cutter rotational speed exceeds about 600 rpm, it is difficult to retain the cutting teeth in their holders, even using retaining springs.
Other attempts to counteract the cutting drum slowdown problem include adding torque to the hydrostatic system and increasing kinetic energy through increasing the mass of the cutting drum. For example, lead is added to the interior of the cutting drum to increase its mass and reduce the elasticity inherent in a hydraulic system.
It is often the case that the number of depressions in a given rumble strip and/or the size of the depressions in a given rumble strip are different depending on the job site. Accordingly, in order to accommodate these changes, current practice non-electronic controller systems require the replacement of the cutting drum and/or a complete change of the mechanical control mechanism (eccentric wheel, cam/lever) in order to achieve the required depression sizing. Such reconfiguring of the cutting machine is time consuming and costly, making an electronically controlled unit desirable. In addition, it is also desirable to make these cuts as rapidly as possible.
Thus, there is a continuous need for improved designs for cutting tools to increase operating efficiencies. In particular, there remains a need to maintain cutter rpm throughout the repeating cutting cycle while encountering varying road surface conditions. The present invention fulfills this need, and further provides related advantages.
The present invention provides a cutting machine for cutting depressions in a road surface. The cutting machine includes a rotatable cutting drum connected with a drive device for rotating the cutting drum and an engaging device for moving the cutting drum out of and into contact with the road surface. The drive device includes a gear box with a flywheel located on the input side of the gear box, while the cutting drum comprises a plurality of cutting teeth, the teeth removably positioned to the cutting drum to effectively cut the road surface, and includes a means for anchoring a tooth shank to a tooth holder permanently affixed to the cutting drum.
In one form, a power unit that moves the cutting drum along the road surface is provided with a detector for continuously detecting a distance that the cutting drum is moved by the power unit and for generating a signal indicative of the distance moved. An electronic controller, responsive to the signal, electronically controls the engaging device so that the cutting drum moves out of and into contact with the road surface in accordance with the distance that the cutting drum moves along the road surface and a specified dimensional profile of the depressions which are stored in the electronic controller. The movement of the cutting drum cuts depressions in the road. An optional means is provided to prevent rear end skidding which can cause cutting drum tracking problems.
The present invention provides means for electronically controlling the vertical motion of the cutting drum of a cutting machine and automatically adjusting the cutting drum to align with the contours of the road surface as it travels over the road surface. Both of these features allow the cutting process to progress more quickly and accurately than previous road cutting machines because they impose no limitations on the depression forming production rate beyond the cutting time required by the cutting drum.
The present invention also provides a cutting machine which electronically controls the vertical movement of the cutting drum into and out of contact with a road surface, thereby allowing a power unit and the cutting drum to continuously progress forward as the cutting drum cuts depressions.
The present invention further provides a cutting drum machine which maintains cutter rotational speed above a minimum speed required throughout the repeating cutting cycle as it encounters varying road surface conditions.
The cutting machine for cutting depressions in a road surface as set forth in the present invention includes a rotatable cutting drum; a plurality of cutting teeth, the teeth removably retained to the cutting drum to effectively cut the road surface; a drive system for rotating the cutting drum and maintaining the rotational speed to provide at least one full revolution at a pre-selected depth of cut, wherein the drive system includes a gear box comprising a flywheel on an input side of the gearbox; engaging means for moving the cutting drum out of and into contact with the road surface; means for moving the cutting drum along the road surface; means for continuously detecting-the distance that the cutting drum is moved by the moving means and for generating a signal indicative of the distance moved; electronic control means, responsive to the signal, for electronically controlling the engaging means to move the cutting drum out of and into contact with the road surface in accordance with the distance that the cutting drum moves along the road surface and a specified dimensional profile of the depressions which are stored in the electronic control means so that the depressions are cut, and means for continuously aligning the cutting drum with a slope of the road surface.
The invention optionally provides electronic feedback relative to movements of the cutting drum, which feedback can be processed and displayed to the operator periodically, thereby alerting him as to whether or not the cutting drum is operating properly, that is, has sufficient time to complete the cutting cycle in relation to the forward speed of the entire cutting machine.
The invention utilizes as much weight a possible to keep the cutting drum engaged with the road surface.
The invention also provides means for both electronically and mechanically adjusting the cutting tool to vary both the depth and width of the depressions consistently across the length of the rumble strip as well as to vary the depth and width of the depressions across the length of the rumble strip, as field conditions or job specifications require.
An advantage of the present invention is that the flywheel boosts the torque applied to the cutting drum to keep it from slowing down as the cutting drum engages the road surface during a cut. This allows the mobile power unit to travel at a higher rate of speed, thereby allowing the cutting drum to make more cuts in a unit of time.
Another advantage of the present invention is that the cutting teeth design of the present invention are retained in their holders at the rotational speed of the cutting drum as the cuts are made.
Other objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description and drawings. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not limitation. Many changes and modifications within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications.